The greenhouse effect of CO2 has been pointed out as a cause of global warming, and there is a pressing need to take a measure against the greenhouse effect internationally from the viewpoint of saving the global environment. CO2 emission sources include various fields of human activity where fossil fuels are burned, and there is a tendency towards an ever-increasing demand for the suppression of CO2 emissions. This has led to an energetic study on a method, for power generation facilities such as thermal power plants and the like that use a large amount of fossil fuels, that includes bringing a flue gas from boilers into contact with an amine-based absorbent such as an aqueous amine compound solution to remove and recover CO2 from the flue gas.
When CO2 is recovered using the absorbent from the flue gas, amine compounds disadvantageously accompany a decarbonated flue gas from which CO2 has been recovered. The amount of the amine compound released together with the decarbonated flue gas should be reduced from the viewpoint of preventing the occurrence of air pollution from amine compounds.
Patent Literature 1 discloses a conventional method that provides a water rinsing unit in a plurality of stages that recover amine compounds accompanying a decarbonated flue gas by subjecting a decarbonated flue gas, from which CO2 has been absorbed and removed by gas-liquid contact with an absorbent, to gas-liquid contact with rinsing water, and successively performing treatment for the recovery of amine compounds accompanying the decarbonated flue gas in the water rinsing unit in the plurality of stages. The rinsing water used in Patent Literature 1 is condensed water obtained by condensing and separating the water contained in CO2 in such a treatment that CO2 is removed from an amine-based absorbent with CO2 absorbed therein to regenerate the amine-based absorbent.
Patent Literature 2 discloses a conventional apparatus that includes a cooling unit that cools a decarbonated flue gas from which CO2 has been absorbed and removed by gas-liquid contact with an absorbent, and a contact unit that allows condensed water obtained by condensation in the cooling unit to be brought into countercurrent contact with the decarbonated flue gas. Further, Patent Literature 2 discloses an apparatus including a water rinsing unit that allows a decarbonated flue gas, from which CO2 has been absorbed and removed by gas-liquid contact with an absorbent, to be brought into gas-liquid contact with rising water to recover amine compounds accompanying the decarbonated flue gas. The rinsing water is condensed water obtained by condensation in a cooling tower that cools a flue gas before the recovery of CO2.